you seem a bit blasee about 'whatnot'.
It's not just money you would lose.
If denied entry your passport will more than likely get a 'denied entry' stamp and will also be recorded. You won't just be let back into departures to board the next flight back with a cheery wave and a mild telling off. You and anyone you are travelling with will be detained until you are escorted to the flight
That's if the airline you are using to fly you into Dublin lets you even board if it has doubts you will be able to land there (because they use Timatic).
Sometimes people with less than simple visa needs have to take a more expensive flight routing to avoid any immigration issues.